This investigation is part of an interdisciplinary study of the effects of microclimate on the ecology of arthropod-borne diseases in a rapidly changing tropical environment as a result of construction of a hydroelectric dam. The dam is now being constructed in the Bayano River, some 70 Kms. east of the Pacific entrance to the Panama Canal. Impoundment will start early in 1975 and when flooding is completed a lake some 60 Kms, in length and 300 Km2 in surface area will be formed. Within the region to be flooded there is a high point which will become an island after impoundment of the river. It is on this future island that a main camp and laboratory have been established for an ecological study of arthropod-borne diseases. On-site microclimate stations have already been established at the camp and in a forest tower and canopy forest bridge locations. Microclimate data are to be correlated with those ecological-virological-entomological data being collected in the Bayano River Basis before, during, and after flooding to attempt to show the influence of the microclimate on the epidemiology of arthropod-borne diseases and offer a basis of predictability for similar engineering projects that are being developed in tropical America.